High hopes for heart disease as boffins decode the giraffe genome

It might sound like a tall story, but giraffe genes could one day help humans with heart disease.

A gene which allows giraffes to withstand the high blood pressure their height requires  without severe damage to their cardiovascular system should be a target for research by medical scientists, researchers said this week.

Writing in the journal Science Advances, biologists who introduced giraffe gene mutations into mice found the small rodents suffered less cardiovascular and organ damage than a control group when they were medicated to increase their blood pressure, and grew more compact and denser bones.

“Both of these changes are directly related to the unique physiological features of the giraffe — coping with high blood pressure and maintaining compact and strong bones, despite growing them faster than any other mammal, to form the elongated neck and legs,” said lead author Rasmus Heller, from the University of Copenhagen in Denmark.

Heller’s team worked with biologists from Northwestern Polytechnical University in China to produce a high-quality genome from the Rothschild’s giraffe, mainly found in eastern Uganda and western Kenya, and investigated which genes are likely to be responsible for its unique biological features.

These include blood pressure, which is twice as high as in humans and most other mammals to ensure a steady blood supply to the head.

The team homed in on a gene called FGFRL1, which has evolved much more in giraffes than in many other animals.

The gene is “strongly selected” in the giraffe, meaning it has had a powerful effect on the animal’s characteristics, or phenotype.

A University of Copenhagen statement said: “The dual effects of the strongly selected FGFRL1 gene are compatible with the phenomenon that one gene can affect several different aspects of the phenotype, so called evolutionary pleiotropy.

“Pleiotropy is particularly relevant for explaining unusually large phenotypic changes, because such changes often require that a suite of traits are changed within a short evolutionary time.

“Therefore, pleiotropy could provide one solution to the riddle of how evolution could achieve the many co-dependent changes needed to form an animal as extreme as a giraffe.

“Furthermore, the findings even identify FGFRL1 as a possible target of research in human cardiovascular disease.”

Heller’s team also found genes regulating circadian rhythm and sleep were “under strong selection in giraffes, possibly allowing the animals a more interrupted sleep-wake cycle than other mammals”.

Standing up is a complicated procedure for a giraffe and because this makes them vulnerable to predators, they have evolved to spend much less time sleeping than other mammals, sometimes as little as 30 minutes a day.

In line with research in other animals, an evolutionary trade-off also seems to have determined the strength of their senses.

“Giraffes are in general very alert and exploit their height advantage to scan the horizon using their excellent eyesight,” said Heller.

“Conversely, they have lost many genes related to olfaction, which is probably related to a radically diluted presence of scents at five metres compared to ground level.”

Another lead author, Qiang Qiu, from Northwestern Polytechnical University, said the results showed animals could be useful in helping biologists understand “which genes influence some of the phenotypes we are really interested in, such as those related to disease”.

Five giraffe facts you may not know

1. The blood pressure of a giraffe is about 280/180mmHg. Ideal blood pressure in humans is considered to be between 90/60mmHg and 120/80mmHg.

2. The giraffe’s black tongue is believed to be an adaptation to protect it from sun exposure during the time it spends browsing for food.

3. Collective nouns for a group of giraffes include herd, kaleidoscope, journey and tower.

4. An adult Rothschild’s giraffe, such as the male that supplied genetic material for the new research, eats about 34kg of food daily to support a body that weighs up to 1,100kg.

5. Giraffes give birth standing up. The newborn’s fall helps to break the amniotic sac, and the mother and baby are safer from predators than they would be if birth took place lying down.